Children with juvenile idiopathic arthritis (JIA) experience fluctuating pain, stiffness and fatigue as a consequence of their disease. In spite of advances in medical therapy including the widespread use of methotrexate and biologic medications, pain persists as an unexpectedly common problem for children with JIA. We have previously shown that children with polyarticular arthritis experience pain on a majority (70%) of days with substantial adverse consequences such as interference with age appropriate social, academic, and physical functioning. Yet little is known about the daily patterns, moderators, and consequences of persistent pain in these children. We propose to use real-time assessments via electronic diaries to elucidate the pain experience of children with JIA and the moment-to-moment impact of child emotion regulation and caregiver response on pain-related disability. Seventy-five children with polyarticular JIA aged 8 to 16 will be recruited from the pediatric rheumatology clinic at Duke University Medical Center to participate in this study along with their primary caregiver. Consenting families will complete baseline and 3-month follow-up measures of pain, psychosocial adjustment, emotion regulation, and physical function and be trained in the use of electronic diaries on handheld computers for daily data collection. Following baseline assessment, children will complete three momentary assessments per day for two 14-day time periods assessing pain quality, current emotional state, and functioning across school, social, and physical domains. Similarly, primary caregivers will complete three momentary assessments on the same days as their children reporting their responses to child pain. We expect that pain will predict moment-to-moment functioning. However, we anticipate that successful child emotion regulation (within-day recovery from aversive emotional states or maintenance of desirable emotional states) and empowering responses by caregivers (responses that promote child emotion regulation) will lessen the extent to which pain leads to functional impairment in children with JIA. Results of this study will highlight areas for intervention to prevent pain-related disability in children with JIA, potentially reducing health care costs and enhancing quality of life for these children and their families. Symptom capture using the electronic diary methodology employed in the proposed study also may prove to be useful for assessing the effectiveness of therapeutic interventions in both individual patients and clinical trials. PUBLIC HEALTH RELEVANCE: Children with juvenile idiopathic arthritis have pain despite new therapies. We propose to capture daily symptoms using electronic diary data collection symptom. This will result in significant contributions both to the theoretical understanding of the pain experience of children with JIA and how to intervene to prevent pain- related disability. Data may support aggressive pain control in children with this disease and suggest individualized treatment approaches for self-management of a child's pain at any given. Moreover, the innovative methodology proposed in this study for evaluating emotion regulation can expand the broader field of child development research, bridging research interests in child development, childhood chronic illness and child pain. Finally, the study can serve as a catalyst for future research aimed at advancing medical and psychological knowledge of pain in other pediatric medical populations.